In general, the invention relates to methods and compositions for the generation and use of conformation-specific antibodies or fragments thereof.
Protein phosphorylation is a key cellular signaling mechanism that induces changes in protein conformation. For example, the phosphorylation of specific serine or threonine residues that immediately precede a proline residue (Ser/Thr-Pro motif) is a central regulatory mechanism in the cell. The unique stereochemistry of the proline residue means that the peptidyl-prolyl bond of the Ser/Thr-Pro motif can adopt two different conformational states (i.e., a cis conformation or a trans conformation). Peptidyl-prolyl cis/trans isomerases (PPIases) specifically catalyze the cis/trans isomerization of Ser/Thr-Pro motifs and, thus, regulate the structure of these proteins between the two distinct conformations.
Pin1 is a PPIase that specifically catalyzes the cis/trans isomerization of certain phosphorylated Ser/Thr-Pro (pSer/Thr-Pro) motifs. The identification of Pin1 as a phosphorylation-specific PPIase led to the understanding of a new signaling mechanism, whereby Pin1 catalytically regulates the conformation of its substrates after their phosphorylation to further control protein function. Moreover, Pin1 is tightly regulated by multiple mechanisms, and the deregulation of Pin1 plays a pivotal role in some human diseases.
The prevalence of Alzheimer's disease (AD) may quadruple worldwide by 2050, but currently there is no effective treatment. The AD hallmark lesions in the brain are senile plaques made of Aβ peptides and neurofibrillary tangles of phosphorylated tau (p-tau). Tau-related pathology (tauopathy) correlates well with progressive loss of neurons and memory in AD and is also a defining feature of many other tauopathies without Aβ pathology. While active and passive immunization against Aβ peptides have reached clinical trials, immunotherapy against p-tau has fallen far behind. Recent findings that active or passive immunization against tangle-containing p-tau epitopes reduces tau aggregates and improves memory deficits in mouse models and that tauopathy can spread the disease from neuron to neuron suggest that p-tau immunotherapy is a promising new approach to treating AD. However, since neuronal dysfunction occurs long before tangle formation, a major challenge is the development of immunotherapy targeting only the early pathogenic events that lead to tauopathy and memory loss in AD.
A very early event in tauopathy of AD is tau hyperphosphorylation notably on Ser/Thr-Pro motifs, which causes microtubule disruption and neurotoxicity. It has been found that phosphorylated Thr231-Pro motif in tau (pT231-tau) exists in the two distinct cis and trans conformations, and the prolyl isomerase Pin1 accelerates their conversion to inhibit tauopathy. Pin1-null mice displayed age-dependent tauopathy, whereas Pin1 overexpression inhibits tauopathy in a mouse model of AD. In human MCI and AD neurons, Pin1 is inhibited by multiple mechanisms, whereas the Pin1 SNP that prevents its down-regulation is associated with delayed AD onset. It has also been found that human Pin1 located at 19p13.2 is associated with late-onset AD, that pT231-tau is at the beginning of sequential p-tau epitopes in pretangle neurons, and that CSF pT231-tau is an early biomarker that correlates with memory loss and tracks MCI conversion to AD, and distinguishes AD from frontotemporal dementia (FTD). Thus, pT231-tau is a very early disease-initiating event in AD.
Veteran soldiers returning from war experience distinctive traumatic brain injury (TBI) features that are the same as neurodegenerative disease reported previously in athletes who have sustained multiple concussions. It appears that TBI in these people can trigger the development of chronic traumatic encephalopathy (CTE), a devastating neurodegenerative disorder, for which there is no known treatment. The neuropathological hallmark of CTE is the widespread abnormal accumulation of hyperphosphorylated tau (p-tau) as neurofibrillary tangles (tauopathy), similar to the hallmark lesion seen in Alzheimer's disease (AD) and other tauopathies. Thus, immunotherapy against p-tau is proving to be a new option for treating tauopathies. More specifically, there exists a need in the art for conformation-specific antibodies that specifically bind to a cis or trans conformation of p-tau to target the early pathogenic pretangle tau modifications leading to tauopathy.